The evaporative system typically comprises several banks of material to be wetted (also called: material banks), a water reservoir and a hydraulic device with a pump for moving the water from the water reservoir to the top of the material banks to wet the material. The banks of material to be wetted and the water reservoir are mounted inside the air duct of the air conditioning system. As air passes through the wetted material in the air duct, moisture is evaporated into the air flow. Mats of polyester fibres or glass fibres may for example be used as material, with one block of mats constituting one material bank.
FIG. 1 shows an evaporative system 1 according to the state of the art with material banks 2, a water reservoir 4 placed below the material banks 2 and a hydraulic device 5 in an air duct 3 of an air conditioning system. The material banks 2 extend in the transverse direction to the air flow. Water outlets of the hydraulic device are connected with the top of the material banks 2 via hoses/pipes 6. The hydraulic device 5 is connected to the water reservoir 4. The hydraulic device 5 typically consists of several single, separate components including among others a pump, tubing, an outlet valve for each material bank. The pump and the outlet valves are not individually adjustable such that water supply to the material banks cannot be varied apart from altering the states of the outlet valves or manually replacing mechanical flow restrictors. The valves can only be operated in one of two states: open or closed.
The hydraulic device 5 according to the state of the art needs to be mounted onto the water reservoir 4 inside the air duct 3. The hydraulic device 5 may thus block air flow in the air duct 3 leading to a decrease in energy efficacy. Furthermore, access limitations and/or legislation in some markets (such as Underwriters Laboratories UL 998) may require mounting the hydraulic device outside the air duct.